1. Field of the Invention
This invention relates to an alarm annunciator and, more particularly, to a system for providing audible coded alarm signals indicative of the occurrence of certain nonstandard conditions. By way of illustration, the system might be used in a warehouse or factory to indicate various types of nonstandard conditions such as: Excessive heat; open flame; an open door or window; a water leak; movement in an area that should be uninhabited; a malfunctioning machine or process; or any of a wide variety of other conditions that should be made known and/or might require corrective action.
2. Description of the Prior Art
A wide variety of features have been provided in prior art systems. In some systems, the nonstandard condition responsive means includes a mechanical mechanism for generating a unique code which results in audible signals. In other systems, the nonstandard sensing means places a potential indicative of the nonstandard condition on a lead. In response to the presence of this potential, a unique code indicative of the nature and location of the nonstandard condition may be generated.
Systems of the first type may be defined as station coded alarm systems. In such systems, if two nonstandard conditions should develop simultaneously, a garbled and nonsense alarm code may be generated. This condition is particularly aggravated if common audible means are used.
Systems of the second type usually provide lockout means to prevent overlapping or garbled codes. Such systems may also include means for preventing retransmission of an alarm code without a reset signal and/or for locking in an alarm condition signal even though the nonstandard condition may have existed only momentarily.
Sometimes, it is desirable to be able to have a system which uses commom audible alarms and which uses sensing means which produce a station coded signal together with station means which apply a potential indicative of the nonstandard condition. In such systems, the receipt of a station coded alarm during the transmission of another alarm can result in garbled codes so that neither alarm code is intelligible.